Field of the Invention
The present invention relates to a bridge circuit for switching high currents, having n (n=a natural integer) lowside and highside switches in the form of vertically structured MOS transistors on two separate chips. The highside switch is formed using DMOS technology.
Such a bridge circuit is typically used in order to drive motors during direct-current and pulse-width-modulated operation, or to switch valves. The bridge circuit can be produced using different numbers of switches, with a halfbridge being produced if n=1, a full bridge or H-bridge being produced if n=2, a three-phase bridge being produced if n=3. An n-phase bridge is produced in the case of n.
A bridge circuit as mentioned above has become known heretofore from German patent DE 196 95 582 C1. There, all the switches of the bridge circuit, that is to say the lowside switches in addition to the highside switches, are formed using DMOS technology. In order to allow control at a high current level, the chips are arranged one above the other using so-called chip-on-chip mounting. The load paths of two mutually associated transistors are connected in series by virtue of the mounting. One embodiment provides for two highside transistors integrated on a common chip, and two lowside transistors on separate chips. The chip-on-chip mounting of that prior art bridge circuit is a relatively complicated process which, in particular, requires complicated bonding. Furthermore, it is known for bridge circuits to be produced as monolithic circuits for use with low currents, in particular using BCD-MOS technology. The major disadvantage of this implementation is the relatively low operating currents.
Finally, it is also known for the bridge circuit to be produced with discrete power transistors, that is to say with four power transistors for an H bridge circuit and a driver circuit in addition, which is either constructed from discrete components or is designed to be integrated. The discrete construction of the circuit variant admittedly allows large current loads to be switched, but it is time-consuming and occupies a large amount of space.